INHIBITION OF TUMOR-GROWTH BY PEPTIDE-SPECIFIC CYTOTOXIC T-LYMPHOCYTES IN A 3-DIMENSIONAL COLLAGEN MATRIX

Tumor associated, MHC I restricted antigenic peptides have been identi fied in both human and mouse tumors. Cytotoxic T lymphocytes (CTL) whi ch recognize these tumor associated antigenic peptides are potential a nti-cancer effecters. The anti-tumor activity of CTL is usually measur ed in vitro by the Cr-51 release assay and in mice by tumor growth inh ibition which is the most direct assessment of anti-tumor effect. In c linical studies, an in vivo tumor growth inhibition assay is not an op tion and an in vitro assay which corroborates with in vivo tumor growt h is needed to assess the long-term outcome of CTL activity. Here, a t hree-dimensional (3-D) collagen gel assay was developed to measure in vitro the inhibition of mouse mammary tumor growth by anti-tumor CTL. BALB/c mouse CTL were induced with peptide E474 SFAVATTAL which was ex pressed by mouse mammary tumor cells D2F2. To measure D2F2 tumor growt h inhibition in vitro, a mixture of tumor cells and anti-E474 CTL in a 1 mu l cell bolus was embedded in the collagen gel. Complete eradicat ion of tumor growth was observed at E:T ratio of or greater than 1:1. rIL-2 supplementation was necessary to achieve long-term tumor growth inhibition. Even spontaneous D2 tumor explant could be grown in the co llagen gel and addition of anti-E474 to this culture reduced tumor gro wth. This assay system provides a realistic and sensitive alternative to the in vivo tumor growth inhibition assay and allows easy adaptatio n to test additional therapeutic reagents.